It is often necessary or desirable to measure the amount of material stored in a tank. This may be useful, for example, during loading of material into the tank or unloading of material from the tank. As particular examples, “custody transfers” and “weights and measures” often require highly accurate measurements from level gauging instruments installed on the roof of a tank.
Different types of level sensors can employ different types of measurement techniques to identify the level of material in a tank, such as ultrasonic, capacitive, optical, and microwave measurement techniques. Microwave-type level sensors typically transmit microwave signals at the material in a tank through free space or through a wire or other conductive structure and use reflections of the microwave signals to identify the top surface of the material in the tank. The latter approach is often referred to as guided wave radar (GWR).